U.S. Pat. No. 4,315,086 discloses, as compatibilizing agents for polyamides and polyphenylene ethers, liquid diene polymers, epoxy compounds and compounds having in the molecule beth (a) carbon-carbon double bond or carbon-carbon triple bond and (b) carboxylic acid group, acid anhydride group, acid amide group, imide group, carboxylate group, amino group or hydroxyl group. The above patent further discloses, as impact strength modifiers, ethylene propylene rubbers, ethylene propylene polyene rubbers or these rubbers modified with unsaturated carboxylic acids, SBR, polybutadienes, diblock copolymers or triblock copolymers of polystyrene-diene rubbers and partial hydrogenated products thereof.
Japanese Patent Kokai Nos. 59-59724 and 59-86653, U.S. Pat. No. 4,654,405 and PCT Laid-Open Application WO87/00540 disclose processes for producing compositions by grafting unsaturated carboxylic acids on polyphenylene ethers in the presence or absence of free-radical initiators and then mixing polyamides with the products.
EPC Laid-Open Application EP-0046040 discloses alkenyl aromatic compounds, .alpha.,.beta.-unsaturated dicarboxylic acid anhydrides or imide compounds thereof as compatibilizing agents for polypheylene ethers and polyamides.
PCT Laid-Open Application WO85-05372 discloses aliphatic polycarboxylic acids such as malic acid, U.S. Pat. No. 4,659,760 discloses polyethylene oxide waxes, U.S. Pat. No. 4,659,763 discloses quinones, U.S. Pat. No. 4,732,937 discloses polyphenylene ethers made functional by epoxy compounds, and U.S. Pat. No. 4,600,741 discloses polyfunctional compounds comprising anhydrotrimellitic acid chloride as compatibilizing agents for polyphenylene ethers and polyamides. These compounds all can be used as compatibilizing agents in the present invention as mentioned hereinafter.
Japanese Patent Kokai Nos. 63-108060 and 63-113071 and PCT Laid-Open Application WO88/06173 disclose compositions comprising combination of non-crystalline polyamides with compatibilizing agents, polyphenylene ethers and crystalline polyamides.
In the conventional processes, there has not yet been found optimum structures of thermoplastic resin compositions comprising of polyphenylene ethers and polyamides in which A--B--A block copolymers containing styrene are used as impact strength modifiers.
In conventional processes, the styrene-containing A--B--A block copolymers (especially, styrene-butadiene-styrene copolymers) are present in a sufficiently dispersed state in polyphenylene ethers. (See FIG. 3)
FIG. 3 (Prior Art) is a transmission electron photomicrograph of the composition of Comparative Example 4 which shows the structure where polyphenylene ether (grey spheres) is dispersed in matrix (white) and rubber particles (black) are dispersed in the form of lumps in the polyphenylene ether.
When the dispersion has such a structure, the effect of impact strength improvers is lowered. Increases in the amount of impact strength modifiers for improving impact strength brings about deterioration of heat resistance. When the amount of polyphenylene ether is increased for inhibiting the deterioration of heat resistance, flowability decreases and moldability deteriorates.